Why does a water turbine on the roof pneumatic valve vacuum damage

vacuum breaker pneumatic valve & #; Pneumatic valve is a kind of security. Mainly used for vessel or pipe, in a pipe or container due to system run or stop the negative pressure or vacuum gradually rise, the pneumatic valve can automatically open, destroy the vacuum effect, pipelines and other equipment will not produce the phenomenon such as flat, concave cracks, in order to protect the safety of equipment.
why does a water turbine on the roof vacuum breaker pneumatic valve?
when turbine need emergency stop, guide vane quickly closed truncation to enter the water wheel, at this point, the water behind the due to inertia effect to continue through the tail pipe that the lower part of the top part of the vacuum cavity, and this part of the vacuum and quickly fill up with draft tube flow back water back. When water flow back back flow rate quickly, the powerful high-speed flow have a great impact, sometimes the runner up and cause damage to the parts. To solve this problem, should be installed on the roof of vacuum pneumatic valve. Emergency shut down, when the guide vane on the roof cavity formed by vacuum, because of the top air pressure difference inside and outside, the vacuum breaker pneumatic valve pneumatic valve body is pushed to the side of mobile, vacuum pneumatic valve open the lower part of introducing air into the top, make the vacuum breaker, in order to prevent the accident.
vacuum breaker general pneumatic valve installed on the turbine top cover ( A) either upstream or downstream Like farmer with straw hat shape. When the turbine guide vane was suddenly closed, turbine indoor vacuum formed, causing negative water hammer ( Water flow backward into the runner room) , easy to broken drum lid of turbine running water or lighter unit lifting machine damage equipment. When a vacuum, atmospheric pressure to overcome the force of the spring in the vacuum breaker pneumatic valve, pneumatic valve pneumatic vacuum to undermine the body open, to fill gas destroying the vacuum. When the vacuum after the destruction of the same as the atmospheric pressure, under the action of the spring shut down automatically, complete a vacuum action. （ Its security pneumatic valve)